A new study published in The British Medical Journal, which sourced dietary information from a number of low, middle, and high-income countries, found that consuming a high number of refined grains, such as those present in croissants and white bread, is associated ith a higher risk of major cardiovascular disease, stroke, and early death.
 
The study, called PURE (Prospective Urban Rural Epidemiology), has been examining diets from diverse populations across the world. Over 16 years, the study tracked the diets and health outcomes of 137,130 participants in 21 countries, including Canada, with results suggesting that the consumption of refined grains and added sugars has increased greatly over the years the study has been active.
 
Grains were categorized into three groups: refined grains, whole grains, and white rice. Refined grains included goods made with refined flour, including white bread, pasta/noodles, breakfast cereals, crackers, and bakery products/desserts containing refined grains. Whole grains included whole grain flours such as buckwheat, and intact or cracked whole grains, such as steel cut oats.
 
The study found that having more than seven servings of refined grains per day was associated with a 27% greater risk for early death, a 33% greater risk for heart disease, and a 47% greater risk for stroke. There was no elevated risk for significant adverse health effects associated with the consumption of either white rice or whole grains, however.
 
“This study reaffirms previous work indicating a healthy diet includes limiting overly processed and refined foods,” Scott Lear, Simon Fraser University health sciences professor, said.  
 
“Refined grains have lower dietary fiber content, vitamins and minerals, essential fatty acids, and phytochemicals, largely owing to loss of the outer bran layer and the endosperm of the grain being pounded during the process of refining,” the authors of the study said. “As a consequence of the refining process, rapid action by digestive enzymes and quick absorption from the small intestines could lead to an increase in post-prandial blood glucose concentrations. The rise in glucose concentrations increases the insulin concentrations, which leads to hypoglycaemia, lipolysis, and the stimulation of hunger and food intake.”
 
While white rice is technically considered a refined grain generally, the fact that it was not associated with health risks to the same degree as other refined grains could be due to its more favorable glycemic effects, in addition to the fact that, depending on the culture in question, white rice could be serving as a replacement to less favorable foods, the authors said.
 
“Intakes of a combination of cereal grains with a lower intake of refined wheat products should be encouraged while promoting a higher intake of whole grains,” the authors of the study concluded. “Reduction in quantity and improvement in quality of carbohydrate is essential for better health outcomes.”